Preparation for painting the exterior an underneath

The body shop doing my Mustang likes soda blasting and chemical stripping.

Soda blasting - Removes paint well and doesn't damage panels, but won't remove rust.

Chemical stripping - very effective at removing paint. Tape off body seams so you don't get stripper in there. Chemically strip the large areas and manually remove paint from edges/seams. Lots of horror stories of stripper getting into seams and crevices where it can't be completely removed, only to later ruin your fresh new paint job. This is the method the shop used on my Mustang because the soda blasting service they usually use wasn't available.

Acid dipping - Effective at removing all paint, rust and scale, and thoroughly cleans ALL the metal inside and out (think frame rails, etc). BUT, often need to drill holes in various places on the body to allow air to escape when being dipped, so will need to be re-welded; and very difficult to remove all the chemical from the inaccessible areas. Also, lots of stories of 'dipped' cars having residue leak out of cracks and crevices on nice days only to ruin their beautiful new paint jobs. This happened on a co-worker's Austin Healey.

Water/Media blast - The process looks very effective, but the mobile blasters who come do it in your yard or driveway are going to leave one helluva mess when they're done.

Regardless of the process used to strip, be sure to phosphatize the surface right after stripping to protect against flash rust. Tons of overpriced products available such as Eastwood's Metal Prep, however it's just Phosphoric Acid - the same stuff is available from any Home Depot or Lowe's Hardware for less than half the cost.

Hopefully, our resident body men will chime in with their professional opinions.

If its a good, solid car why remove the paint?

Soda blasting is real gentle; so gentle it does not remove filler or rust. I had my car soda blasted then I spend a month in the hot summer with a small bottle blaster re-going over the entire car. You can see some of the rust I was removing after the soda:



Once soda blasted, even the clean areas were not ready for paint. Sand roughs up the surface and makes a tenacious surface to bond too.

I would never dip. I have heard of too many cars which rotted inside out after dipped.

I still would not have an industrial sand blast place do the body, roof, fenders. Everything else is fair game. I sand blasted fenders and body with small bottle blaster but it is so weak compared to the industrial units it's not a problem.



Blasting is a fantastic way to see what repairs your car really needs. If you have access to the car I would not pass up cleaning it up and repairing parts you will no doubt uncover.

Thanks for all of the good information.

Hi Old #7,
I really agree with all Garth's comments.
I'm always very concerned with Chemical / Acid stripping. For the mentioned reasons.

One approach not mentioned yet is media blasting with a plastic and fine sand combination. This is how I had #4042 done. I was extremely satisfied with the result. You can check out the results here...

4042 media blast

One more method not yet mentioned is that of a dry ice blasting. The only residue left afterwords will be the material removed from the material that is blasted.

A quick Google search shows that it will not effectively remove rust, but otherwise it seems to be a promising option.

As it is often used in food processing plants because of it's non-toxic nature, finding a mobile service company should not prove too difficult.

Does anyone know of this method having been used on an auto body?

Larry

Yes.
If you wont to be chore to remove the rust also you have to ADD some fine sand around 10% so it is not only dryice, Then it work weary Well.

Kjeld

old # 7; I had mine media blasted and would do the same again.
Just one add'l item if choosing media blasting- you will have a certain amount of residual media left in the crevices of the body to air "blast" out.

Here is another option, still pricey right now.

https://www.youtube.com/watch?v=dZ_90920Zbg